Light polymerization devices of the type which are operated as hand-held devices typically include a substantially strong light radiation source which emits light radiation that subsequently passes through a light guide, such light polymerization devices serving to polymerize dental materials. The light radiation source is, typically, a light source which is also, however, partially a heat source, whereby the term “light” also comprises ultraviolet radiation.
Such light sources and light radiation sources typically give off heat in the form of heat loss, which must be conducted away from the decidedly compact hand-held device.
In fact, it has already been suggested to provide substantially large cooling ribs around the light source and to rely upon natural convection to ensure the conducting away of heat.
It is precisely with respect to high performance halogen light sources, however, that a cooling approach of this type is not sufficient, whereby, in all such cases, a cooling operation by a fan is provided.
In the prior art, such a fan cooling involves an axial fan deployed for the cooling, whose dimensions are selected in correspondence with the diameter of the housing of the hand-held device so that the cooling air stream flows through the hand-held device substantially parallel to the longitudinal axis thereof. Since it would not be acceptable for a fan to blow air onto the patient treatment location, the air outlet is most often provided on the back side of the housing.
DE-OS 34 11 996 discloses an approach to prevent the result that the fan directly blows onto the dentist applying the treatment or, as the occasion arises, onto the attending dental technician, wherein the air outlet is somewhat downwardly inclined so that the cooling airflow at least is not directed toward the face of the dentist or the dental technician.
The heretofore conventional light polymerization devices having forced cooling characteristically produce, across the full range of such products, an airflow from the patient to the dentist. This means, however, on the one hand, that a significant risk of infection exists for the dentist; at the least, the exhalations of the patient are directly guided toward the dentist.
In order to reduce the risk of infection somewhat, many dentists wear a mouth protector at least during the time of the light polymerization device treatment. This, however, is frequently perceived as unpleasant so that this precautionary measure is, in many instances, not undertaken.
A further problem is the creation of noise from the hand-held device due to the fan operation. With respect to a hand-held device, compact dimensions are desired. Correspondingly, there remains only a decidedly small gap available for the fan airflow. A particular problem is the reflector associated with the light source of the light polymerization device. The reflector has a conventionally known conical form and its outer diameter is only somewhat relatively smaller than the inner diameter of the housing.
At the particular location of the reflector, only a small annular gap is available which thus raises the necessity of a high flow velocity and, consequently, the creation of a comparatively large noise condition. Moreover, a substantially strong fan must be deployed in order to achieve a sufficient cooling in spite of this flow resistance. This fan brings with it not only the necessity of a rapid discharge of the storage battery power supply but, additionally, brings with it the generation of a decidedly strong noise condition.
In order, nonetheless, to make possible a practical working time, it is disclosed in U.S. Pat. No. 5,471,129 to use a substantially large storage battery power supply which, at the same time, is user-friendly in that it lowers the center of mass of the hand-held device, the storage battery power supply being received in the pistol grip of the hand-held device.
Such an approach, in fact, reduces the disadvantage of shortened storage battery power supply time associated with other conventional light polymerization device hand-held devices. The hand-held device is, however, significantly heavy and, consequently, less amenable to a user-friendly hand-held device operation.
A further problem of the known light polymerization devices, which is linked with the afore-described problems, lies in the comparatively reduced effective cooling efficiency. While the cooling air passing through the annular gap around the reflector—that is, around the outer circumference of the reflector—exhibits a substantially high flow velocity, the respective flow velocity and, consequently, the respective cooling effectiveness, is lower at precisely the location of the highest temperature—namely, in the vicinity of the filament.
In order to compensate for this disadvantageous impact, two measures had been suggested: on the one hand, cooling ribs for the cooling body have been extended around the entire reflector so that they reach even to the annular gap. This approach improves, in fact, the cooling effectiveness substantially but, however, requires the production of a difficult to manufacture and comparatively heavy reflector.
The other approach provides for a reduction in the flow cross-section in the region of the filament—namely, on the back side of the reflector. In this manner, the flow velocity is also comparatively high at that location and an improved cooling is possible. A disadvantage of this approach is, however, that the flow resistance in total increases still further so that, while the cooling effectiveness improves, the flow resistance also, however, increases.